1. Field of the Invention
The present invention relates to a process for the preparation of composite material formed from a vulcanized elastomer, containing carboxylic acid or dicarboxylic acid anhydride groups, in combination with a thermoplastic elastomer containing polyamide blocks. It also relates to the composite material composed of a vulcanized elastomer in combination with a thermoplastic elastomer containing polyamide blocks and sports articles, in particular the soles of sports shoes, at least partly composed of such a material.
2. Description of Prior Art
The processes most commonly used for joining synthetic or natural vulcanized elastomer with thermoplastics comprise several time-consuming steps which are difficult to automate:
vulcanization of the elastomer part (by injection molding, compression etc.), PA1 combining of its surface, PA1 halogenation by treatment with a solution of chlorinated polyolefins and drying, PA1 application of a two-component adhesive generally based on polyurethane, and PA1 molding of the rubber with the thermoplastic. PA1 (1) Sulfur-based systems composed of sulfur in combination with the usual accelerators, such as the metal salts of dithiocarbamates (zinc dimethyldithiocarbamate, tellurium dimethyldithiocarbamate, etc.), thiuram disulfides (thiuram tetramethyl disulfide, etc.), sulferamides, etc. PA1 (2) Sulfur-donor systems in which the majority of the sulfur used for curing originates from sulfur-containing molecules such as the organosulfur compounds mentioned above. PA1 (3) Systems based on phenolic resins, composed of difunctional formophenolic resins, which may be halogenated, in combination with accelerators such as stannous chloride or zinc oxide. PA1 (4) Systems based on peroxides. All free-radical donors may be used (dicumyl peroxides, etc. ) in combination with zinc oxide and stearic acid. PA1 1. Polyamide blocks with diamine chain ends with polyoxyalkylene blocks with dicarboxylic chain ends. PA1 2. Polyamide blocks with dicarboxylic chain ends with polyoxyalkylene blocks with diamine chain ends obtained by cyanoethylation and hydrogenation of aliphatic alpha,omega-dihydroxylated polyoxyalkylene blocks termed polyetherdiols. PA1 3. Polyamide blocks with dicarboxylic chain ends with polyetherdiols, the polyetheramides obtained being, in this particular case, polyetheresteramides. PA1 Vulcanization time (min)=t.sub.90 +(E/2-2)
These parts composed of an elastomer/thermoplastic assembly are used in particular in the shoe industry, in particular for high-quality sports shoes.
However, significant savings at the process level could be achieved by omitting some of the operations described above, in particular the entire section relating to the application of the adhesive.
The reactivity of some elastomers with polymers based on polyetheresteramide is also known. Thus, Japanese Patent JP 63 081159 (DW 88-038019/20) describes a thermoplastic elastomer composition composed of a polyetheresteramide component and an elastomer having at least one polar group, such as a carboxylic radical. Amongst these elastomers, acrylic elastomers, elastomers based on butadiene and acrylonitrile (nitrile elastomer) and fluorinated elastomers (propylene/tetrafluoroethylene) may be mentioned. These thermoplastic elastomer compositions have a high flexibility, a good resistance to oil and a high mechanical strength.